1. Field of the Invention
The present invention relates to a data driver and a display device and a method for controlling the data driver.
2. Related Art
Conventionally, as a liquid-crystal panel (an electro-optical device) used for an electronic apparatus such as a mobile phone, it is known to utilize a passive matrix liquid-crystal panel and an active matrix liquid-crystal panel which employs a switching element such as a thin film transistor (abridged as TFT).
Compared to the active matrix method, the passive matrix method has an advantage, in that power consumption can be easily lowered, while it has a disadvantage in that colorization and image display are difficult. In contrast, the active matrix method has an advantage in that it is suited for colorization and image display, while it has a disadvantage in that it is difficult to lower the power consumption.
Then, recently, in order to provide high-quality images for the mobile telephones and mobile electronic apparatuses, demands for colorization and image display are becoming stronger. Therefore, the active matrix liquid-crystal panel is now coming into more use than the passive matrix liquid-crystal panel.
Now, with the active matrix liquid-crystal panel, it is preferable that it be provided with an operational amplifier which operates as an output buffer inside a data driver for driving data lines of the crystal panel. The operational amplifier has a high driving capacity and can stably supply voltage to the data lines.
The recent demands for high-quality display images have helped progress in multi-level gray scale and reduction of voltage to be applied to liquid crystal. However, variations in voltages applied to liquid crystal have a large influence on the display quality.
In addition, there are also variations in threshold voltages of transistors composing the operational amplifier which is provided at each data line inside a data driver. Therefore, differences occur in output voltages among the operational amplifiers within the same IC, and, thus, there are cases in which the variations in the voltages applied to liquid crystal influence on the display quality.
In view of the above technical issues, the present invention aims to provide a data driver having a simple configuration which prevents degradation of the display quality created by the variation in output voltages at each data line, a display device, and a method for controlling the data driver.